Process of making artificial wool



v. R. HARDY PROCESS QF MAKING ARTIFICIAL WOOL Sept. 15, 1942.

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Vernal B. Hardy, Wilmington, Del., assigner to E. I. du Pont de Nemours Company, Wilmington, Del., a corporation of Delaware appuemonlusrcn 1s, 19m-serai No. 324,847

s claims (cris- 54) This invention relates to synthetic ilbers and more particularly to artificial wool. t

This invention is an improvement in the method of making artiiicial wool from synthetic linear superpolymers as described in application Serial No. 183,922 filed January '1, 1938, by J. B. Miles and myself. The invention in that application is based on the discovery that synthetic linear polymer nlaments when cold drawn while wet with water or other mildswelling agent, and then dried -while in relaxed condition crimpspontaneously to a product which `is remarkably woollike. This `synthetic wool is superior to those heretofore known in strength, especially wet strength, crimp retentivity =both wet and dry. elasticity, heat stability, and heat insulating properties. These crimped iibers were obtained by avprocess wherein suitably treated wet fibers crimped spontaneously during drying in therelaxed condition. One method for rendering the iibers susceptible to spontaneous crimping consisted ln giving undrawn or partly drawn wet l'aments of the `polymera heat treatment (conver sion) in a suitable medium such as oil, followed by further cold drawing. Another method consisted in simply preparing filaments of the polymer by melt spinning, followed by wetting and cold drawing the laments. This last mentioned method, which is referred yto as the "direct spinning process, in addition to giving abetter product, would be the more economical and convenlent process were it not for certain restrictions which have seriously handicapped this method.- The most serious of the restrictions are that the n process requires the use of polymers of low viscosity, which means that the bers have a lower tensile strength than those made from higher viscosity polymers, and the process requires lower spinning temperatures than are consistent with eiiicient melt spinning; VA further disadvantage is that it is dillicult to reproducel results, i. e. obtain products of uniform quality from run to run.

This invention has as an object a new and improved ,method for the manufacture of articial Wool. A further object is the preparation of crimped iibers by an improved direct spinning process which is free from the disadvantages noted above. More specifically an object of this invention is to provide a processfor melt spinning fiber-forming syntheticlinear polymers susceptible'to cold drawing, whether of low or high viscosity, which will impart spontaneous crimping properties to the resultant filaments. Other objects will appear hereinafter.

The above objects are accomplishedtby spin-` ning from melt a. syntheticlinear polymer, which can be formed into illainents susceptible to cold drawing, e. g.` crystalline synthetic fiber-forming i have formulated that the ability of a synthetic I discovered further that low, medium, or even.

linear polymer i'llament to crimp spontaneously after being cold-drawn Wet and allowed to dry is dependent upon large diierences in the sizes "of the crystals in the iilament. This theory is based on the following observations: An examination of a cross-sectional photo-mcrograph of yarn, which is spun from low viscosity polyhexamethylene adipamide at the usual spinning temf perature (for instance about'28`3" C. in the mjelt and 270 C. atthe spinneret) vand which is incapable of spontaneous crimping, revealed that the crystallites in the laments of the yarn are so small as to be invisible and are presumably of relatively uniform size. a similar photo-fmicrograph of yarn spun from the same polymer but at thelower spinning temperature required to produce a .spontaneous crimpable yarn revealed that crystal growth had Aproceeded to the point where many of thecrystals were visible under the microscope and that the crystals were extremely non-uniform in size throughout the individual iilaments. I observed .further that when a medium or high viscosity polymer is melt spun in the usual method, even though the lowest practical temperature is used.

the filaments are not spontaneouslycrimpable to f any appreciable extent and appearl under the 4microscope similar to those in a yarn obtained from low viscosity polymer at high temperature.

high viscosity polymer, when spun from melt under the conditions described below for controlling the rate of cooling gave spontaneously crimpable filaments `which showed marked nonuniformity oi crystal size when' examined under the microscope. Z

The slowl cooling of the extruded 'filaments brought about by the practice of this invention allows for the non-uniform crystal'growth which -I have found to characterize the spontaneously crimpable filaments.` The most effective andi-v On the other hand,.

preferred method of practicing my invention consists in passing the laments directly after extrusion from melt, i. e. on leaving the spin,

neret, through a zone of gas or vapor, the temperature of which is well above room temperature, namely, at least '75 C., but not higher than about 25 C. below the melting point of the polymer. The preferred temperature and length of the heated zone will dependupon such factors as the melting point of the polymer, the viscosity of the polymer, the denierJ of the iilaments spun, and the speed of spinning. If the polymer viscosity or the spinning temperature or both are only slightly above those best suited for the production of spontaneously crimpable filaments, the heated zone may be relatively short and of low temperature. If, on the other extreme, the polymer viscosity or the spinning temperature or both are far above those best suited for their production of spontaneously crimpabie yarn, the heated zone must be longer and of aDhigher temperature in order to effect the desired results. The most suitable length and temperature for the heating zone are also dependent upon the spinning wind-up speed and the filament denier. As the spinning wind-up speed is increased, other things being constant, it is desirable to lengthen the heating zone or increase its temperature, or both. On the other 1iancl, as the filament denier is increased. the necessity for retarded cooling in order to produce spontaneous crirnpability is decreased. In most instances the temperature will be within the range of from 75 C. upto about 25 C; below the melting point of the polymer, although in rare instances it may be in the range from 50 C. up to 10 C. below the melting point of the polymer. The length of the heated zone through which the lament passes will in general be such that the lament will be exposed to the heated zone for from 0.02 second to 0.2 second but in some cases the time of exposure may range from 0.01 to 1.0V second. Depending on the spinning speed the length of the heated zone will generally 'range from 1 to 5 feet. The heated zone need not have a uniform temperature, in fact, it is desirable that the portion of the zone close to the spinneret have a higher temperature than the portion farthest removed from the spinneret. The iilamentary stream of molten laments solidify during their passage through the heated zone.

Suitable apparatus for carrying out my invention is shown in the accompanying drawing in which Fig. 1 is a front elevation of a heated chimney with a spinneret associated therewith;

Fig. 2 isa plan view of the chimney shown in Fig. 1;

Fig. 3 is a longitudintal sectional view; and

Fig. 4 is a front elevation of -another form of chimney.

The chimney shown in Figs. 1, 2 and 3 is about 18" high and is 4" square and is constructed ofa suitable metal such as galvanized iron. The entire front consists of a door I hinged at 2 and provided with a 2 x 2l window 3. A similar window may be -mounted in the opposite wall. The chimney about 2" from its top is provided with an inlet for a thermometer 4. On the inner side of each of the opposite walls 5 and 6 are resistance coils 1. The top of each' coil is about 2" from the top of the chimney and the terminal ends 8 of the coil about the same distance from the bottom. The resistance coil is designed to carry 50, 100 or 200 watts for heating. Any temperature may be obtained between room temperature and 1'90" C. within 2" from the top. The temperature at approximately 4" from the bottom may vary between room temperature and '75 C.

The upper end of the chimney fits tightly 'I against the bottom of the spinneret assembly The spinneret.

l l2 which abut the spinneret plate 9 and with a thermocouple well i3 adjacent the spinneret plate. The body of the spinneret block Il is also'provided with aninlet for a thermometer 25. The filaments 22 extruded through the plurality of holes in the spinneret plate unite to a single yarn 23 which is drawn around the roll 2t by a wind-up roll not shown.

Fig. 4 shows a chimney of similar construction having a door Ul hinged at vI5 andprovided with latches 2| vand Window I6. 'Ihis chimney is about 7 square and 24 long. This chimney as well as that illustrated in Figs. 1-3, is preferably of insulated construction which may consist of an inner wall Il, and insulating material i8 betweenthe inner wall I1 and outer wall i9. Strip heaters 20 of conventional type are located on three sides of the chimney near the bottom. By this construction the operator may obtain practically uniform temperature throughout the chimney.

Due to the difliculties involved it is not practical to determine the actual temperature of the molten filaments as they leave the spinneret. The spinneret temperatures given below are those obtained from the thermocouple in the Well I3 shown in the spinneret block near the spinneret. This temperature is believed to be somewhat below that of the molten polymer passing through the spinneret orices. The melter temperature is that fof a grid (not shown in the gures) which melts the polymer above the spinneret and spinneret block and from which the molten polymer iiows down through the spinneret block to the spinneret.

This invention is further illustrated in the examples given below. In Examples I-V, in-

clusive, the linear poly-mer is' the polyamide,

polyhexamethylene adipamide, and in Example VI it is polydecamethylene adipamide. The chimney shown in Figs. 1 to 3 was used in the iirst four examples and that shown in Fig. 4 in the'last two examples.

Example I Polmer having a melt viscosity of 200 poises at 285 C. was spun under the following conditions: Melter temperature, 270 C.; spinneret temperature, 262 C.; heating zone temperature "ments `with water and allowed to dry showed very good agaeaaoa f as the undravirnfilaments` are substantially un`" oriented.` The ill nt as used herein Example n The spinning conditions were as follows: melt viscosity of thepolymer, 600 poises at 285 C.;

melter *temperature 269 C.:- spinneret temperature,v258 C.; heating chimney temperature two v inchesfrom the spinneret, 180 C.:V heating chimnew teinperature 14 inches from the spinneret. 70 C.; spinning wind-up speed, 800 ItJminnte;

' yarn spun, 70 denier, 5 laments. The resultant yarn,` when cold drawn 200% while wet'with water and allowed to dry under no tension, showed excellent spontaneous crimping properties. When the'same-polymer wasspun without `the heated zone but otherwise treated under thev samelconditions, it showed practically no spon- `taneous -crimping properties.

Example' 111" The spinning conditions were as follows: melt lviscositypf the polymer, 130poises. at 285 C.;

melter temperature, 279 C.; spinneret temperature, 267 C.; chimney temperature 2 inches below `the spinneret, 215 C.; spinning wind-up speed,"1200 tJminute; yarn spun, 224 denier,

' 15 iilaments. The yarn produced in this way showed excellent crimping properties whenl cold drawn while wet with a swelling agent followed f by drying in the relaxed condition. Yarn spun yfrom the same polymer without the use of the heated zone but otherwise treated inthe same manner, showed `very poor crimping properties.

Example IV refers to both"oriented and uhoriented threads which are drawn'from the polymer. regardless of whether thethreads are long (continuous)` v or short (staple), while the term ffberl refers more specifically to the oriented tllaients. Particularly useful are the polymers obtainable from self-polymerization ofv amino acids or their` amide-forming derivatives, e. g. the lactams, or by reacting a `diamine with a dibasic carboxylic acid orv its amide-forming derivative. These I polymers are described in U. S. Patents 2,071,253

andv 2,130,948. It is to. be understood that the term polymer includes interpolymers obtained from a mixture of diierent linear polymer- The spinning conditions were'as follows: melt viscosity of the polymer, 130 poises at 285 C.; melter temperature, l276. C.; spinneret temperature, 266 C.; heated zone temperature 2 inches below spinneret, 170 C.; spinning wind-up speed, 22(l ,0 ft./minute;l yarn spun, 92 denier, l5 fila- This yarn when cold drawn while wet crimping properties.

Example V The' spinning conditions were as follows: melt viscosity of the polymer,V 160 poises at V285 C.; melter temperature, 278 C.; spinneret temperature, 265 C.; spinning wind-up speed, 1200 ft./minute; yarn spun, 270 denier, 10 filaments. The chimney was used with temperature of 75 C.

cold drawn while wet with water and then dried in the relaxed condition..

Example VI The spinning conditions were as follows: melter temperature, 255 C.; spinneret temperture, 240

Y C.; spinning'wind-up speed, 900 ft./n1i`nute; yarn spun, 150. denier, 10 filaments. The heated zone had a temperature of 125 C. throughout-itsl length. The yarn spun showed excellent spontaneous crimping properties when cold drawn while wet with water followed'by drying under no tension.

This invention is in general applicable to any synthetic polymer capable of being' spun from inelt Vinto lilainents which can be cold drawn. Examplesof polymersof this kind are given in U. S. Patents 2,071,250 and 2,153,553 and in the above mentioned application. These polymers can lie-spun intolaments which yield oriented fibers up'in application of stress herein referred to as` cold-drawing.

Cold -drawn bers show' denite orientation along the ber axis where `throughout its length. The yarn spun showed `excellent spontaneous crimping properties when forming reactants'and thatgthe term polyamide includes interpolyamides and all linear polymers containing a plurality of amide groups as an 'integral part of the main chain of atoms making up the polymer chain, as for instance the ester-amide interpolymers. 'Specic examples of polymers other than that mentioned in the examples which are of particular value inthe practice of this invention are polypentamethylene sebacamide, polyhexamethylene sebacamide, poly-p-xylylene sebacamide, and polymeric S-aminocaproic acid, The polymers may be modiiied with plasticizers, dyes, pigments, inert inorganic materials, resins, etc. as desired.

The optimum degree to which the filaments are cold drawn prior to crimping will dilfer with diierent polymers. y'Preferably the laments are not cold drawn to the maximum extent possible.

300%. The cold drawing can be do'ne'in` stages vif desired. As already indicated, the filaments? are cold drawn ,while wet with a mild swelling agentjtherefor. The preferred swelling agents are low-boiling, hydroxy-containing compounds such as water and theV lower boiling aliphaticalcohols, e. g. methanol, ethano1,` propanol, iso--v propanol, and isobutanol.

Wool-like synthetic polymer filaments can bev prepared of almost any diameter by this process, but laments having deniers 4in the neighborhood of 2 to 25 aremost useful. The crimps producedjn these laments by the spontaneous crimping process are very irregular and wool- Some of them are large, I some small, and they may be either helical or like in appearance.

tion can be applied to polymers having an even wider viscosity range, e. g., from 50 poises to 1000 poises. The intrinsic viscosity of the polymers can also vary over a wide range, e. g. from 0.5 to 1.5. Spinning speeds' ranging fromBOO to 2200 feet per minute were used in the examples but the process is not limited to spinning speeds within this range. peratures Vused may likewise vary widely, de-

' pending upon the melting point and thermal stability ofthe polymer. As previously stated, the

For most filaments, the optimum l degree of cold drawing will vary from to The crimp retentlvity of the.

The spinning tem- Y they have been crimpedrfan if desired be treated with steam, oil or a spinning nish without affecting materially the subsequent crimp-x y ing operation.

'Ihe type of apparatus used to produce the heated zone is not critical. The essential requirement is that a. heated zone be produced.

This may evenbe accomplished by enclosing the area below the spinneret in such a way that thev air Within is warmed by the spinning unit itself or by the molten polymer as it leaves the spinneret. The atmosphere of the heated zone may be air or any inert gas or vapor, e. g. nitrogen, carbon dioxide, or carbon tetrachloride. By practicing the slow cooling technic ,of this invention it is possible to produce spontaneous crimpable yarn from polymers which would not produce such yarn under otherwise comparable conditions. For example, a low viscosity polymer can be spunat advantageously higher temperatures than would otherwise be permissible, or a, higherviscosity polymer` may be used than would ordinarily give the desired results. Or both of these conditions are permissible when the process of this invention is applied. In other words, the spinning temperature and the viscosity of the polymer are much less critical forming synthetic linear polymers spontaneously crimpable upon cold drawing them while wet with a mild swelling agent and then drying them in the relaxed condition, said process comprising extruding the molten polymer through a' spinneret, and preventing rapid cooling of the resultant filaments by passing them after leaving the spinneret and before and during solidiflcation through a heated zone of gaseous medium having a temperature of at least 50 C. but not greater than about 10 C. below the melting point of the polymer.

3. The process for making filaments of fiberforming synthetic linear polymers spontaneously crimpable upon cold drawing them while wet, with water and then drying them in the relaxed condition, said process comprising extruding the molten polymer through a spinneret in filamentary form, and preventing rapid cooling of the filaments .by passing them, after leaving the spinneret and before and during solidiiication,

than in the direct spinning method described in application Serial No. 183,922.

The Wool filaments prepared by the process of this invention resemble those described in the above mentioned application VThat isythey have good elastic properties, show fiber orientation when examined by X-rays, are quite insensitive to moisture, have good resistance to solvents and chemical reagents, are mothproof, have excellent crimp'retentivity and show little tendency to lose strength on aging. The process by which the artificial fibers of this invention are made is of such a character that modifying ers, can be readily incorporated therewith The fibers of this invention can be made either as long (continuous) fibers or can be cut into short (staple) 'fibers They are useful for` making knitted or woven fabrics, rugs, felts, and the like. If desired, the iibers and yarns can be mixed with other fibers and yarns, for example, viscose rayon, acetate rayon, cotton, silk, and wool.

As many apparently widely diiierent embodiments of this invention may be made .without departing from the spirit and scope thereof, it

vis to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claims.

I claim:

1. In a process for making crimped filaments from a. melt-spinnable, crystalline synthetic linear polymer, the step comprising extruding the molten polymer through a spinneret into a heated zone, of gaseous medium which is maintained at a temperature of at least 50 C. but

agents, for example, delusterants and plasticizthrough aheated zone of gaseous medium for a time of from about .02 second to 0.2 second, said zone having a temperature of at least C. but not higher than 25 C. below the melting point of the polymer.

4. A process for producing spontaneously crimpable filaments which comprises extruding molten synthetic linear fiber-forming polymer through a spinneret, preventing rapid cooling of the resultant filaments by passing them, after leaving the spinneret and before and during solidication, through a zone of gaseous medium having a temperature of at least about 75 C. but not greater than about 25 C. below the melting point of the polymer for a time from about .02 second to about 0.2 second, wetting the filaments with Water, cold drawing the wet filaments, and drying the filaments in a relaxed condition.

5. The process set forth in claim 2 in which said polymer is a polyamide.

6. The process set vforth in claim 4 in which said polymer is a polyamide.

7. The process as set forth in claim 4, in which said polymer is polyhexamethylene adipamide.

8. In a. process for producing crimped laments, the steps comprising extruding molten synthetic linear fiber-forming polymer through v 

